The present invention relates to environmental control systems for aircraft and enclosed spaces. More particularly, the invention details a hybrid vapor cycle/air cycle environmental control system (ECS) which provides conditioned, pressurized air to an enclosed space.
Presently, the most common type of air conditioning for aircraft and enclosed spaces, which include a gas turbine engine as a primary power source, is an air cycle environmental control system. Examples of these systems are described in U.S. Pat. Nos. 4,198,830; 4,334,411; and 4,580,406. The systems of these references seek to minimize the quantity of bleed air extracted from the turbine engine while still meeting compartment heating and cooling flow requirements, and compartment pressurization and ventilation flow requirements. Typically, the flow of air required to meet heating or cooling needs is greater than that required to meet pressurization and ventilation requirements. However, if the supply air temperature to the compartment to be cooled can be reduced sufficiently, then the air flow can be correspondingly reduced to the level demanded by the requirement for ventilation and pressurization. The reduced bleed air flow extraction from the turbine engine is reflected in reduced fuel consumption or greater available power.
Heretofore, attempts to combine air cycle and vapor cycle concepts have resulted in cumbersome systems that were either just an air cycle and a vapor cycle system separately installed or were integrated systems that would not provide a continued flow of air to the compartment in the event of a failure in the vapor cycle loop.
The present invention efficiently integrates the vapor cycle loop with the air cycle components so as to minimize the total number of system components and the weight and size of the resulting system and also provides a system that is capable of continuing to deliver the critical required pressurization and ventilation air flow in the event of failure of any component within the vapor cycle loop. The complete system minimizes the extraction of bleed air from the gas turbine engine, utilizes that bleed air so as to provide the maximum contribution to the total cooling need, and provides the additional cooling needed by means of an efficient vapor cycle loop.